1. Field of the Invention
This invention relates in general to position indicating devices and more particularly to position indicating devices for use with hand operated tube benders and the like.
2. Prior Art
The need to field fabricate thin walled electrical conduit, small watering lines, etc. of varying lengths and shapes led to the development of the tube benders. However, the principal problem with the tube benders has been the inability to accurately duplicate bends. To solve this difficulty, a whole range of angles indicating means have been incorporated in tool benders. For example, Gardner U.S. Pat. No. 2,932,225 issued Apr. 12, 1960 and entitled "Tubing Bending Device" discloses an adjustable straight spirit level attached to the bending head of the bender. Benfield et al U.S. Pat. No. 3,063,314 issued Nov. 13, 1962 and entitled "Pipe and Tube Bender" simply employed markings on the bending head, while Benfield U.S. Pat. No. 3,253,441 issued May 31, 1966 and entitled "Pipe Bending Tool" discloses a free swinging pointer attached to the shank of the tube bender that aligns with markings on the arcuate shaped bending head. In another alternate Linquist U.S. Pat. No. 4,009,602 issued Mar. 1, 1977 and entitled "Tube Bending Tool with Angle Sighting Means" utilizes a sighting tube attached to the bending head to help the operator see the angle markings on the bending head. The difficulties with all of the above prior art devices are that they depend upon operator sightings from a distance of four or five feet. This is simply to far for accurate measurement during field use since the markings on the bending head are so small. In one alternative, Brown U.S. Pat. No. 2,953,048 issued Sept. 20, 1960 and entitled "Angle-Indicating Attachment For A Pipe Bender" utilized an arcuate angle indicating means whose pointer movement is controlled by a linkage means attached to or positioned on the pipe being bent. Such a device could be attached closer to the operator on the bender handle, but in addition to being more complex and thus more likely to be broken during field use it is not readily adaptable to bending short pieces of pipe. Because of the difficulty in designing an accurate tube bender more recent developments have centered around tube benders where the operator pre-sets a desired angle by mechanical means. Examples of such devices can be seen in Benfield U.S. Pat. No. 3,718,018 issued Feb. 27, 1973 and entitled "Pipe Bending Tool"; Crouse U.S. Pat. No. 3,906,778 issued Sept. 23, 1975 and entitled "Pipe and Tube Bender"; Mount U.S. Pat. No. 4,052,881 issued Oct. 11, 1977 and entitled "Improved Process for Providing Offset Bends of the Correct Dimension in Pipe and the Like" and Nason U.S. Pat. No. 4,321,820 issued Mar. 30, 1982 and entitled "Pipe-Bending Tool." While these tools work fine when the exact angle of bend is known, prior to bending they become more cumbersome to use when the exact angle is not known, as more than one adjustment must be made. In addition, these tools are more complex and thus expensive. Thus, in spite of the extensive research and development there still exists the need for a simple tube bender that allows variable accurate tube bending in the field.